Stabilization of cyanogen chloride



Patented Aug. 2 8, 1951 STABILIZATION F CYANOGEN, CHLORID Morris S. Kharasch, Chicago, 111., assignor to the United States of America as represented by the Secretary of War No Drawing. Application April 2, 1946,

,Serial No. 659,136

The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to the stabilization of commercial cyanogen chloride and particularly to stabilization under normal storage and shipping conditions.

The objects of this invention include a stabilized cyanogen chloride composition and a method for preparing the same.

Previous investigators have very difficult to stabilize cyanogen chloride unless the latter were absolutely pure. One proposal, that of Guy H. Buchanan, U. S. Patent 1,586,175, employs hydrogen cyanide as a stabilizer for liquid cyanogen chloride. There have also been other proposals for purifying cyanogen chloride in order that the product might be more stable.

While pyrophosphoric acid has been considered found that it was as a stabilizer for hydrogen peroxide, the problem of stabilizing cyanogen chloride, a non-oxygencontaining compound which tends to polymerize and to hydrolyze, is entirely non-analogous.

Cyanogen chloride is an effective fumigant and has other uses. It is unstable in steel containers, particularly in the presence of impurities, such as water. In the presence of alkalies, or acids, cyanogen chloride tends to decompose. Polymerization also occurs, yielding, among other products, cyanuric chloride and cyanuric acid. It is therefore very diiiicult to stabilize cyanogen chloride, particularly the commercial product which contains impurities and which has been, or is to be, in contact with ferrous metal containers.

I have discovered that it is possible to stabilize cyanogen chloride, which may contain water, hydrogen cyanide, hydrogen chloride and soluble iron salts as impurities, by adding a pyrophosphate, particularly an alkali metal pyrophosphate thereto. Limiting the water content, further aids in stabilization.

The cyanogen chloride produced in this country keeps well at elevated temperatures when stored in sealed glass tubes in the absence of steel. The effect of impurities in decreasing the stability of the cyanogen chloride in the presence of iron or steel is probably due to the formation of soluble iron compounds. The impurities present in the cyanogen chloride currently produced are: (1) hydrogen cyanide, (2) water, (3) hydrogen chloride, (4) soluble iron salts. Hydrogen cyanide in concentrations 0.3% to 2.35% has little or no effect on the stability of this product.

It is of the utmost importance to bear in mind that the lower the water content of the cyanogen chloride, the greater the stability of this material when aged in steel containers, and the greater the effectiveness of the substance used to stabilize it. The water content of the cyanogen chloride 8 Claims. (01. 23-14) should not exceed 0.2%, eentages of water up to 0.4% for military use.

The following table gives the efiectiveness of various stabilizers at four difierent temperatures. The water content of the cyanogen chloride used in these tests varied between 0.15% and 0.35%.

TABLE I Stabilization of cyanogen chloride [Days for complete solidification in the presence of steel] for best results. Per.-

can be tolerated Temperature Control GaO KF N 214F20 (2% CaO) (2% KF) (2% NalPzoi) (5% CaO) (5% KF) (5% N84P201) 1, 1.5 3, 5, 3.5 2.5, 2.5 174, 209

(5% 02.0) (5% KF) (5% NaAPIO'I) Commercial sodium pyrophosphate is the best stabilizer yet found. Material conforming to the following specifications gives excellent and repro-' Surveillance of cyanogen chloride with water added [Temperature l00.]

Days for Stabilizing Amount of Stab1- Km and steel sta e... sra Remarks N o stabilizer or steel 40, 40 0.3 g. steel (control). 4, 7 5% NmPzOH-OB g.

steel 209, 209 202, 202

No stabilizer or steel ll, 12 .2% Hi0 added. 0.3 g. steel (control). 7, 7 Do. 5% NB4P207+0.3 g.

steel 89, 89 82, 82 Do.

N o stabilizer or steel 8, l2 .5% H2O added. 0.3 g. steel (control). 3, 6 Do. flIP201+0.3 g.

steel 15, 15 9, 9 D0.

never been stored in iron were aged in glass at 65 C. without agitation. To each 25 m1. lot was added a single strip (4" x bomb steel. In some instances, of weight of anhydrous tetrasodium pyrophosphate (stabilizer) was added to each lot of cyanogen chloride before the aging was commenced. After varying lengths of time, the tubes were opened and their contents filtered through a porous porcelain plate. The filtrate was divided into 3 ml. samples and each sample was aged in glass at 125 C; without agitation. In some instances, a strip of bomb steel (2" x was added to these small samples, and in some instances, a similar strip and 5% by weight of ium pyrophosphate.

TABLE III Stability of cyanogen chloride at .125 C. Before and after storage at 65 0. Samples not agitated I claimi 1. A stabilized composition, comprising cyanogen chloride and a pyrophosphate as the stabilizing agent.

2. A stabilized composition, comprising cyano gen chloride and an alkali metal pyrophosphate as the stabilizing agent.

3. A stabilized composition, comprising cyanogen chloride and sodium pyrophosphate as the stabilizing agent.

4. A stabilized composition, comprising cyanogen chloride and 2 to 5% of anhydrous tetrasodium pyrophosphate as the stabilizing agent.

5. A stabilized composition, comprising cyanogen chloride, not more than 2% of water and a pyrophosphate as the stabilizing agent.

6. A stabilized composition, comprising cyanogen chloride, not more than 2% of water and'an alkali metal pyrophosphate as the stabilizing agent.

7. A stabilized composition, comprising cyanogen chloride, not more than .2% of water and sodium pyrophosphate as the stabilizing agent.

solidification Times (Days) in Glass Analysis Storage Conditions of Cyanogen Chloride Used in 125 Surveillance No steel or Steel but no Steel and Fe,

' stabilizer stabilizer Stabilizer Per SN YR H20 H Cl HON present present Present Cent Cyanogen Chloride Not Aged 20. 0, 23. 0 1. 5. l. 5 64, 82 08 10 days in presence of steel at 65 7. 0, 7. 0 l. 5, l. 5 77' I 008 .05' 20 days inpresence of steel at 65. 6. 7. 0 l. 5. 1.5 50, 64 012 .073 087 days in presence of steel at 65. 6. 0, 6. 0 1. 6. 1.5 68, 70 019 095 061 days in presence of steel at 65 4. 0, 4. 0 1.5, 1.5 60 .022 13 .08 10 days in presence of steel and stabilizer at 65 10. 0. 16.0 V 1.5.1. 5 52, 52 .008 055 .053 20 days in presence of steel and stabilizer at 65. 79, 79 2. 0, 2. 0 77, 79 007 036 026 30 days in presence of steel and stabilizer at 65- 52, 68 2.0. 2. 0 68, 68 0056 .054 020 40 days in presence of steel and stabilizer at 65. 59.' 59 1.5, 1.5 43,' 9 .008 012 1 Soluble non volatile residue. Examination of this data discloses in every in- 8. A stabilized composition, comprising cyanoof the pyrophosphate.

Of all the su V pyrophosphate (NaiPzoq) in 2 to 5% by weight is the most effective stabilizer of the cyanogen chloride, currently produced in this. country. Other yrophosphates, particularly alkali metal pyrophosphates, may'also' be used however. Anhystance an enormous stabilizing eifeet on the part bstances tested, anhydrous sodium drous' tetrasodium pyrophosphate has been accepted by the ,CWS as the standard stabilizing agent for cyanogen chloride.

It will be understood that the foregoing de-. scriptive matter and specific examples are to be interpreted as illustrative and are not to be construed in a limiting sense.

gen chloride, not more than .2% of water and '2 to 5% of anhydrous tetrasodium pyrophosphate- REFERENCES CITED The following references file of this patent UN TED S T T Name Date Walker Mar. 19, 1940 Number are of record in the 

4. A STABILIZED COMPOSITION, COMPRISING CYANOGEN CHLORIDE 2 TO 5% OF ANHYDROUS TETRASODIUM PYROPHOSPHATE AS THE STABILIZING AGENT. 